1. Field of the Invention
The present invention relates to a semiconductor module such as an MCP (Module Chip Package) in which a semiconductor chip is mounted on a module substrate and is molded in a resin.
2. Description of the Background Art
A semiconductor memory device is utilized in a personal computer, a workstation and the like in some cases. In addition, in recent years the speed, degree of compactness and number of functions of personal computers have increased and, therefore, semiconductor memory devices have been required to further increase their memory capacity. In addition, the market has expanded so that a large number of low-cost memory devices are used. Therefore, further increase in the capacity of, and further reduction in costs of, semiconductor memory devices have become required.
The number of DRAMs (Dynamic Random Access Memory), from among the above described semiconductor memory devices, utilized in personal computers or the like has increased because it is advantageous from the point of view of cost per bit unit. Cost per bit unit can be reduced by increasing the diameter of wafers even in the case that the capacity is increased and, therefore, DRAMs are frequently utilized.
In a DRAM, however, cost of development, cost for high level institutions, and the like, have greatly increased together with the increase in the testing period of time and test costs accompanying the increase in capacity as well as the enhancement of microscopic processing technology so that whether or not those costs can be reduced has become a problem.
The bit configuration for the input to or output from a DRAM is conventionally 4 bits, 8 bits or 16 bits. Therefore, the variety in types of bit numbers is small. Accordingly, one module is made up of a plurality of DRAMs for general utilization. Thus, a semiconductor memory device such as a DRAM is, in many cases, utilized in a module condition.
FIGS. 27 and 28 show an example of a conventional semiconductor module (memory module). The conventional semiconductor module has a structure, wherein single chips 117, in which bare chips 101, mounting islands 118, bonding wires 105 and lead frames 110 are molded into mold resin 108, are mounted on both, front and rear, sides of a module substrate 102, such as of an SOP (Small Outline Package) or a TSOP (Thin Small Outline Package) corresponding to a surface mounting technology wherein parts can be mounted on both sides of a printed circuit board.
In addition, development has progressed of a memory package having a basic tendency toward miniaturization and thinning together with enhancement of performance and of functions of a memory chip. Then, though an insertion system was adopted for a memory package, in recent years the forms of packages have greatly changed such that a surface mounting system has been adopted.
At present, the surface mounting system has become the main trend in place of the insertion system and further miniaturization and lightening of a package are strongly required. Up to the present, simplification of design and increase in reliability, as well as reduction in cost, have been achieved by utilizing a semiconductor module
In addition, in a conventional manufacturing process of a semiconductor module, in the case that a defective chip is discovered in a module test after the manufacture of a semiconductor module, testing and replacement of such a defective chip are carried out until such defect has been removed.
As described above, there is a problem with the conventional semiconductor module wherein a plurality of single memory chip ICs (Integration Circuits) in the form of packaged single chips 117 are mounted on semiconductor module substrate 102, as shown in FIGS. 27 and 28, and therefore, the mounting area of the single memory chip ICs becomes large.
Thus, in the present application, the inventors examined the case wherein a plurality of bare chips 101 provided in semiconductor module substrate 102 was integrally covered with mold resin 108, as shown in FIG. 29, thereby enhancement in the degree of compactness of the semiconductor device was achieved.
In the case that the plurality of bare chips 101 provided in semiconductor module substrate 102 is integrally covered, as shown in FIG. 29, with mold resin 108, however, there is a problem wherein a great amount of time and effort are required for the replacement of a memory chip that has been detected as being defective according to the conventional manufacturing process of a semiconductor module. Furthermore, though there is a memory module in the form of a COB (Chip On Board) as a semiconductor module with which high density mounting can easily be carried out, there is a problem wherein a bare chip 101 that has been detected as being defective cannot be repaired after bare chips 101 have been sealed into mold resin 108 according to the conventional module in the form of a COB.
A first object of the present invention is to provide a semiconductor module wherein repair becomes possible by newly mounting a good chip even in the case that a chip defect is detected after the chips have been molded into mold resin.
A method that has been examined by the inventors in this specification, as described above, of repairing a semiconductor module in which a plurality of bare chips are mounted by using a good chip is explained in reference to FIGS. 29 to 32. As shown in FIGS. 29 to 32, a plurality of bare chips (chips in the condition of having been cut out from a wafer) is aligned so that the plurality of bare chips are integrally sealed in mold resin 108. Then, a repair chip mounting region secured for mounting, in the case that there is a defective bare chip 101 on the front surface of semiconductor module substrate 102, a single chip 117, which is a good product, is formed on the rear surface of semiconductor module substrate 102 in which the plurality of bare chips 101 are molded. A single chip 117, wherein a conventional bare chip, alone, is sealed into a mold having a lead frame, is usually mounted in the above region.
In such a case as is described above, however, the pitch between the plurality of bare chips 101 and the pitch between a plurality of single chips 117 mounted as repair chips (single molded product) differ from each other as shown in FIG. 32. Therefore, the number of bare chips 101 that can be mounted on the front surface of semiconductor module substrate 102 and the number of single chips 117 that can be mounted on the rear surface differ from each other.
Accordingly, semiconductor module substrate 102 is considered to have a structure wherein, in the case that a plurality of bare chips 101 from among the entirety of the plurality of bare chips 101 becomes defective, there is a case wherein a plurality of single chips 117 that performs substitute functions cannot, depending on the combination of that plurality of defective bare chips 101, be mounted. For example, a case can be considered wherein semiconductor module substrate 102 has a structure on which single chips 117, respectively, that substitute for two bare chips 101 adjoining each other, respectively, cannot be mounted.
In addition, semiconductor module substrate 102 is, for example, considered to have a structure wherein, in the case that the entirety of the plurality of bare chips 101 mounted on semiconductor module substrate 102 becomes defective, it becomes impossible to mount all of the good chips that perform functions substituting for that entirety of bare chips 101. More concretely, in regard to semiconductor module substrate 102 shown in FIG. 32, in the case that the maximum number of bare chips 101 that can be mounted is 12, only eight single chips 117, at a maximum, can be mounted as repair chips. Accordingly, the entirety of repair chips 103, respectively corresponding to the entirety of bare chips 101, cannot be mounted and, therefore, bare chips 101 remain when the single chips 117 that substitute for corresponding functions cannot be mounted.
A first object of the present invention is to provide a semiconductor module wherein repair becomes possible by newly mounting a good chip even in the case that a chip defect is detected after the chips have been molded into mold resin.
A second object of the present invention is to provide a semiconductor module wherein the semiconductor module can be repaired in the case that any bare chip becomes defective and in the case that any combination of bare chips becomes defective. Thereby, the yield of a semiconductor module as a product is increased.
A semiconductor module of the present invention is provided with a semiconductor module substrate, a plurality of bare chips mounted on the main surface of the semiconductor module substrate, and a mold resin for covering the plurality of bare chips together with the main surface of the semiconductor module substrate. In addition, the semiconductor module substrate includes a plurality of repair chip mounting regions provided outside of the mold resin that are regions wherein repair chips that can be used in place of the plurality of bare chips, respectively, and that have input/output terminals can be mounted. Furthermore, the semiconductor module includes a plurality of electrical wires which, in the case that any of the plurality of bare chips is detected as being defective and a repair chip is mounted on any of the plurality of repair chip mounting regions, is connected to the input/output terminals of the mounted repair chip so that electrical signals that have been inputted to or outputted from the bare chip that has been detected as being defective are inputted to or outputted from the mounted repair chip via the input/output terminals. In addition, the semiconductor module is formed so that the above described plurality of electrical wires is connectable to input/output terminals of a repair chip that is used in place of an arbitrary bare chip selected from among the plurality of bare chips or connectable to respective input/output terminals of a repair chip that is used in place of an arbitrary combination of bare chips, respectively, selected from the plurality of bare chips.
According to the above described configuration, a repair chip can be mounted on any of the plurality of repair chip mounting regions in place of a bare chip that has become defective from among the plurality of bare chips and, thereby, the semiconductor module can be repaired after the bare chips are sealed in resin. Therefore, bare chips other than the bare chip that has become defective from among the plurality of bare chips can be effectively utilized.
Furthermore, the plurality of electrical wires is formed so as to be connectable to input/output terminals of a repair chip that is used in place of an arbitrary bare chip selected from among the plurality of bare chips or connectable to respective input/output terminals of a repair chip that is used in place of an arbitrary combination of bare chips, respectively, selected from the plurality of bare chips. Therefore, the semiconductor module can be repaired in the case that any bare chip from among the plurality of bare chips becomes defective or in the case that any combination of plural bare chips from among the plurality of bare chips becomes defective.
A repair chip of the semiconductor module of the present invention may be a single repair chip wherein a bare chip is sealed in resin and a lead frame is provided. In addition, the semiconductor module may be formed so that, in the case that single repair chips are mounted in an overlapping manner in the direction perpendicular to the main surface of the module substrate so as to have a stacked structure, it is possible to connect the plurality of electrical wires to the input/output terminals of the respective single repair chips in the stacked structure.
According to the above described configuration, the number of single repair chips mounted on the main surface of the semiconductor module substrate can be increased per unit area.
A repair chip of the semiconductor module of the present invention may be a double capacity repair chip having a memory capacity two times as large as that of a bare chip, which is a single repair chip wherein a bare chip is sealed in resin and a lead frame is provided. In addition, the semiconductor module may be formed so that it is possible for the plurality of electrical wires to be connected to the input/output terminals of a double capacity repair chip that is used in place of any two bare chips from among the plurality of bare chips.
According to the above described configuration, the semiconductor module can be repaired when two bare chips have become defective in the case that one double capacity repair chip is mounted and, therefore, labor needed for mounting a repair chip can be reduced.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.